1. Technical Field to Which the Invention Belongs
The present invention relates to a cell gap adjusting device, pressurizing seal device and liquid crystal display device manufacturing method for adjusting a thickness between a pair of substrate plates (hereinafter, referred to as “cell gap”) in a liquid crystal cell.
2. Prior Art
It is a general practice to manufacture a conventionally widespread liquid crystal device by bonding together an opposing pair of substrate plates through a seal member having a frame form and an opening at a predetermined point in a frame wall thereof into a cell, filling a liquid crystal into the cell through the opening in the seal member, and sealing the opening with a seal material. Herein, the method for filling a liquid crystal into the cell broadly uses a so-called vacuum filling method. That is, a chamber having cells arranged is evacuated into a vacuum state, so that, if the atmospheric pressure is restored within the chamber with the opening in the cell seal member immersed in liquid crystal, a pressure difference occurs between the cell and the chamber. As a result, liquid crystal is filled within the cell.
However, where using the above method, liquid crystal may be excessively filled in the cell possibly resulting in a case where the cell gap of the liquid crystal cell is greater than a predetermined thickness (hereinafter, referred to as “target value”). Namely, the substrate plates in the pair are possibly swelled outward (oppositely to the liquid crystal). There has been a problem that an expected display characteristic cannot be obtained in a liquid crystal device using a liquid crystal cell thus increased in cell gap greater than a target value. In order to solve such a problem, it is a general practice to carry out a so-called pressurizing process at a stage where the liquid crystal has been poured but the opening of the seal member is not yet sealed wherein pressure is exerted onto both outer surfaces of the substrate of liquid crystal cell thereby expelling excessive liquid crystal and adjusting the cell gap to a target value.
Herein, FIG. 13 is a sectional view showing one example of a conventional pressurizing device as used in such a pressurizing process. As shown in FIG. 13, conventionally it is a general practice to clamp a liquid crystal cell 1 to be pressurized by a pair of rigid plate-like members 90 and apply a force F to the plate-like members 90 thereby exerting pressure onto the substrate plates 11, 12 of the liquid crystal cell 1.
FIG. 14 is a sectional view showing another example of a conventional pressurizing device. It is noted that this figure shows a case wherein a plurality of liquid crystal cells 1 are to be worked at one time.
As shown in FIG. 14, in the conventional pressurizing device, liquid crystal cells 1 to be worked and interposing papers 91 for impact absorption and protecting the substrate surfaces of the liquid crystal cells 1 are alternately stacked one over another, and these are clamped by rigid plate-like members 90. Then, pressure is exerted onto the plate-like members 90 thereby pressing the substrate plates of each liquid crystal cell 1 at both outer surfaces through the interposing papers 91 thus providing pressurization.
However, the pressurizing device shown in FIG. 13 is structured such that the plate-like members 90 are in direct contact with the substrate surfaces of the liquid crystal cell 1. Consequently, in order to correctly adjust a cell gap in the liquid crystal cell 1, there is a need to make the contact surface a perfect flat surface. However, there is a limit in making the surface of the plate-like member 90 such a perfect flat surface. Currently, some roughness is formed in the surface or the plate-like members 90 are unavoidably uneven in thickness. Thus, there has been a problem that, if the liquid crystal cell 1 is directly pressurized by such imperfect surfaces and the cell gap is not correctly adjusted to a target value, an expected display characteristic is not obtained in the completed liquid crystal device.
Meanwhile, because the pressurizing device shown in FIG. 14 is structured such that the interposing papers 91 are in direct contact with the substrate surfaces of the liquid crystal cells 1, pressure cannot be evenly exerted onto the substrate surfaces of the liquid crystal cells 1 similarly to the pressurizing device shown in FIG. 13. There has been a problem that an expected display characteristic cannot be obtained in the completed liquid crystal device.
Also, in a duration of from starting the pressurizing on the plate-like members 90 to a full contraction of the interposing papers 91, because the pressure on the plate-like members 90 is absorbed by the interposing papers 91, a pressure as expected cannot be exerted onto the substrate surfaces of the liquid crystal cells 1. As a result, there has been a problem that the time the cell gap in the liquid crystal cell 1 reaches a target value is prolonged by an amount of the foregoing period. Furthermore, where the number of liquid crystal cells 1 to be simultaneously worked is increased in order to improve productivity, the number of the interposing papers 91 inserted between the liquid crystal cells is also increased. Thus, the above problem is particularly pronounced.
The present invention has been made in view of the foregoing problems, and it is an object to provide a cell gap adjusting device, pressurizing seal device and liquid crystal display device manufacturing method capable of correctly and swiftly adjusting the cell gap of one or more liquid crystal cells.